In open-end spinning machines, such as are described, e.g., in the handbook "Autocoro" of W. Schlafhorst & Co., a sliver is supplied between a drawing-in roller and a feeding trough to be separated into its individual constituent fibers by an opening cylinder. Debris particles and waste fibers are also separated to a great extent in this process. The opening cylinder transports all such components over a fiber guide surface into the area of a debris exit opening. During this transport, the fibers as well as the debris particles and other waste are accelerated by the opening cylinder and by a current of air circulating with the opening cylinder in very short time period to approximately the circumferential speed of the opening cylinder. The particles having a minimal mass, that is, fibers and debris particles, thereby have the tendency to leave the circular path tangentially as a consequence of the centrifugal force acting on them as soon as the mechanical guidance is interrupted in the area of the debris exit opening of the opening-cylinder housing.
A debris removal device, e.g., in the form of an endless circulating debris conveyor belt, is arranged immediately below the debris exit opening. In order to prevent spinnable fibers from separating from the opening cylinder in the area of the debris exit opening along with the debris particles the debris exit opening is also designed to serve as a intake opening for air to enter into the opening-cylinder housing under the suction or negative pressure conditions created by the rotating opening cylinder. The fibers have a relatively large specific surface area in relation to their relatively low mass. Thus, this air current is directed onto the opening cylinder and thereby pneumatically holds the fibers against and guides them along the opening cylinder. On the other hand, the debris particles, which have a distinctly higher kinetic energy on account of their larger mass, overcome this air current and are cast away tangentially through the debris exit opening onto the debris conveyor belt running therebelow. The debris conveyor belt subsequently transports the separated debris particles to a suction apparatus located at an end of the machine, where they are discarded.
Such mechanical debris removal devices of open-end rotor spinning machines usually consist, as already indicated above, of a guide conduit which runs below the spinning units, is open at the top and in which a debris conveyor belt is guided. The guide conduit is covered in the area of the spinning positions by a cover member of the spinning units. Disadvantageously, however, the debris particles passing through the debris exit openings of the spinning units, especially the lighter weight debris particles, often collect behind these cover elements, which can not be recognized from the outside and also can not be eliminated during the spinning operation.
It has therefore already been suggested that the spinning units be modified in such a manner that the usual cover elements be entirely eliminated or shortened to a sufficient extent that the area of the debris exit openings of the sliver opening devices of the spinning units are readily visible to an operator and can be cleaned from the outside of the machine.
Such spinning units with a readily accessible debris exit area as well as with an associated cleaning device arranged on an automatic service traveler are described in subsequently published German Patent Application P 195 29 654.0. However, in actual practice, even spinning units designed in this manner have a relatively strong tendency to become contaminated. In particular, the open guide conduit of these debris removal devices has proved to be problematic.
Swiss Patent CH 547,873 teaches an open-end spinning machine whose pneumatic debris removal device comprises an essentially closed outlet conduit running the length of the machine. The outlet conduit comprises upper air intake bores in the area of the spinning positions which are closed by a traveling sealing belt into which regulating bores are formed. Thus, in this apparatus the sliver opening devices of the individual spinning positions are successively loaded with suction air via the regulating bores of the sealing belt. Such an apparatus results in a discontinuous removal of debris, which on the whole is not very satisfactory.
A combination of mechanical and pneumatic debris removal is described in German Patent Publication DE-AS 26 34 770. This known device utilizes a rotating debris conveyor belt guided in an open guide conduit for removing coarse debris components and a suction conduit arranged below the debris conveyor belt for receiving the finer debris components. The suction conduit comprises a through slot on its surface which is sealed by the debris conveyor belt. Regulating bores are also arranged in the debris conveyor belt in this device so that, as in the device according to Swiss Patent CH 547,873, the sliver opening devices of the individual spinning positions are successively loaded with suction air. In particular, the discontinuous loading with suction air is supposed to remove the lighter debris components and therewith avoid damaging flocculations. However, the described device has not become accepted in practice.